1. Field of the Invention
The present invention relates to an apparatus and method for measuring the concentration of developer solution in a liquid printer. More particularly, the invention relates to an apparatus and method for measuring the concentration of developer solution in a liquid printer which can prevent a concentration measuring error due to change of the temperature of the developer solution.
2. Description of the Related Art
A general liquid color image forming apparatus includes a photoreceptor web circulating by being supported by rollers, a reset unit, laser scanning units, development units, a drying unit and a transfer unit.
The reset unit includes a discharger for removing an electrostatic latent image by emitting light to the photoreceptor web and a charger for charging the photoreceptor web to a predetermined electric potential.
The four laser scanning units scan color information of yellow (Y), magenta (M), cyan (C) and black (K) onto the photoreceptor web. The four development units provide developers of yellow (Y), magenta (M), cyan (C) and black (K) to the photoreceptor web.
The development units include a developer supply container for supplying developer to the photoreceptor web and a development reservoir for collecting developer falling from the photoreceptor web. In the development reservoir, there are a development roller, a brush roller for removing developer adhering to the development roller, a squeegee roller for separating a liquid carrier component of the developer supplied to the photoreceptor web which is not used for forming an image, and a blade for collecting the carrier component flowing down along the squeegee roller.
The development supply container receives developer solution contained in the development reservoir, liquid carrier component N (norpor), which is solvent, provided from a developer supply module, and toner which is development material or highly concentrated developer. The developer solution contained in the developer supply container is driven by a pump and supplied between the development roller and the photoreceptor web.
To maintain the quality of an image in the above-described general liquid printer, concentration of the developer solution supplied to the photoreceptor web, that is, the ratio of a mixture of the toner and the liquid carrier, must be appropriately maintained.
A conventional developer concentration measuring apparatus includes a film forming module, a light source, a photodetector, a concentration measurement calculation means or module, a lookup table (LUT), and a roller-driving module.
The film forming module includes a container for containing developer solution, so that the developer solution is formed as a thin film having an appropriate thickness on a roller rotatably installed in the container. The roller-driving module rotates the roller at a constant speed. The photodetector is installed to receive light emitted from the light source and reflected off the film on the roller. The concentration-calculation module contains a means for calculating a concentration of the developer solution on the basis of a signal output p from the photodetector, which is typically done from the lookup table.
However, the inventors have found that, when the temperature of the developer solution contained in the container varies due to change of the temperature of surroundings, the signal output from the photodetector changes. The inventors have found that this change occurs because, as the viscosity of the developer solution changes according to the change of the temperature, the thickness of the film formed on the roller rotating at a constant speed varies. Thus, the conventional developer concentration measuring apparatus has a drawback, in that an error is generated in measuring the concentration of developer solution due to the foregoing change of temperature of developer.
To solve the above problem, it is an object of the present invention to provide an apparatus for measuring the concentration of developer solution in a liquid printer, which can accurately measure the concentration of developer by obtaining and utilizing information on the temperature of the developer.
Accordingly, to achieve the above object, there is provided a developer concentration measuring apparatus for a liquid printer, which comprises a container installed so that developer supplied to a photoreceptor web enters and is exhausted, a roller rotatably installed in the container for forming a film of the developer contained in the container on a surface thereof being exposed while rotating, a roller driving module for driving the roller to rotate at a predetermined speed, a light emitting module for emitting a predetermined amount of light to the surface of the roller where the film is formed, a light-receiving module, installed to detect light emitted from the light emitting module and passing through the film, for transmitting a photodetector signal p corresponding to the amount of received light, an additional sensor in the form of a temperature detector for detecting the temperature T of the developer contained in the container; and an improved concentration measuring module or means for measuring the concentration of the developer from information on temperature output is signal from the temperature detector and from the photodetector signal output from the light-receiving module.
Also, to achieve the above object, there is provided a developer solution concentration measuring apparatus which comprises a container installed so that developer supplied to a photoreceptor web enters and is exhausted, a roller rotatably installed in the container for forming a film of the developer contained in the container on a surface thereof being exposed while rotating, a light emitting module for emitting a predetermined amount of light to the surface of the roller where the film is formed, a light-receiving module, installed to detect light emitted from the light emitting module and passing through the film, for transmitting a photodetector signal p corresponding to the amount of received light, a temperature detector for detecting the temperature T of the developer solution contained in the container, a roller driving module for controlling driving of the roller to rotate at a set speed corresponding to the temperature output signal from the temperature detector, and a concentration measuring module for measuring the concentration of the developer, based on the signal output from the light-receiving module.